Magnetic Anisotropy in Organic-Based Magnetic Materials

Here, we present the facile synthesis of a new class of organic-based magnetic nanostructures consisting of nanowires of vanadium tetracyanoethylene (V[TCNE]$_{\mathrm{2}})$ that self-assemble along the ridges of a grooved substrate. These nanowires exhibit uniaxial magnetic anisotropy in direct contrast to the isotropic in-plane response of typical thin-films. Furthermore, the magnetic anisotropy persists to the point of re-coalescence of the nanowires into a thin film, suggesting effects beyond simple shape anisotropy are at work. Moreover, isolated films of the V[TCNE] analog vanadium methyl tricyanoethylene carboxylate show a temperature-dependent switch in the easy axis from in-plane to out of plane, again suggesting underlying effects beyond shape anisotropy. These results introduce a new degree of freedom for organic-based magnetism and spintronics, allowing for the engineering of magnetic anisotropy at nanometer length scales in a material that exhibits both robust room-temperature magnetic order and the benefits of low cost, mechanical flexibility, and facile synthesis found in other organic materials.